The 1965 B body rear end is the best stock rear end housing to use on the 1962 to 1965 B bodies
All the rest of the 1966 and later axle housing , including the 1965 station wagon rear ends, are wider
As far as what your asking on how wide of rims (the offsets will be determine after determining the width ) and what tire size do you want to use?
I would take a carpenter square pushed up against the axle with the brake drum on and measure from the inner surface of it to the narrowest part of the inner wheel wheels on the inside and the outside to determine what wheel width I could use on that car and go from there
The wider the wheel width you use the straighter the section width will be using the same size tire size on different wheel widths
I haven't messed with a 1965 Dodge B body in a long time so I can't really tell you what you want to know exactly
Hopefully some one else with real knowledge on your car will chime in with some helpful advise on this